1. Field of the Invention
The present invention is a novel process for forming glycol bisphosphate compounds.
2. Description of the Prior Art
Glycol bisphosphate compounds are a known class of organophosphorus compounds which are useful, for example, as flame retardants in polymers. These compounds have the general formula ##STR1## where R is hydrocarbyl (e.g., alkyl, aryl, alkaryl, arylalkyl, etc.) and R' is hydrocarbylene (e.g., alkylene, arylene, etc.). For example, R can be phenyl with R' being alkylene, such as ethylene, isopropylene, neopentyl, etc.
This class of compounds may be prepared by reacting a dihydrocarbylhalophosphate (e.g., diphenylchlorophosphate) with a glycol in the presence of an amine as described in Biorg. Khim., 11(6) 845-848 (1985). However, such a route needs to be run at relatively low temperatures (0.degree.-10.degree. C.) in order to achieve good yields. If this reaction is run at room temperature, it has been found that the major product is triphenylphosphate. This reaction also uses equimolar amounts of amine which produces an amine salt which must be filtered from the reaction mixture. Also, a solvent is needed in such a process.
Another approach to making glycol bisphosphate compounds is described in Japanese Patent Publication No. 74 40342 which shows reaction of phosphorus oxytrichloride with a glycol followed by reaction with phenol.
U.S. Pat. No. 3,492,373 teaches condensation of a bisphenol or bisphenol alkane with a monophenol, a phenylphosphorous halide, or a mixture of phenylphosphorous halide and monophenol.
M. Combey et al. in U.S. Pat. No. 3,869,526 speak of formation of bis(phosphates) by one of two methods. The first involves reaction of an alcohol, phenol or both with phosphorus oxychloride and a diol in that order. The second involves transesterification of a triorganophosphate with a diol, polyol or diphenol preferably in the presence of a metallic transesterification catalyst.